Advance of mechanical hand tool technology has gradually adopted electric power as the main driving source of hand tools to replace those driven by pneumatic power to overcome the problem of the pneumatic hand tools of unable to function in high speeds.
However, the mechanical hand tool using the electric power rather than the pneumatic power encounters first a problem of element cooling efficiency. In the past the pneumatic mechanical hand tool can perform heat exchange through working air at the same time without accumulating waste heat in the mechanical hand tool. But the electric mechanical hand tool uses an electric motor to get working power. In the event that the mechanical hand tool does not have a heat convection design the electric motor and other related elements could easily accumulate waste heat and result in abnormal conditions.
Hence, the present mechanical hand tool industry has devoted a great deal of research and efforts trying to improve cooling efficiency of the hand tools. For instance, China patent No. CN201371407Y and European patent No. EP1285727B1 disclose a technique by deploying an air fan in a casing of a mechanical hand tool. However, the air fan mainly aims to provide cooling of a sanding element of the mechanical hand tool by dispersing waste heat generated during high speed spinning of the sanding element. But on the electric hand tool driven electrically, aside from the waste heat generated by the sanding element, the electric motor and its related control module also generate waste heat. If the electric motor and the related control module do not have proper cooling waste heat will accumulate in the casing of the mechanical hand tool and temperature will rise, and could result in the electric motor and the control module unable to function at a desired working temperature, and abnormal operation tends to take place easily.